Long-Term Debt (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Sep. 30, 2024
Debt Instrument
Long-term and short-term debt, combined amount	$ 1,015.0		$ 840.0
Unamortized Debt Issuance Expense	(6.0)		(6.9)
Long-term debt	1,009.0		833.1
7.00% Senior Notes Maturing in March 2030
Debt Instrument
Long-Term Debt, Gross	840.0		840.0
Revolving Credit Facility
Debt Instrument
Maximum borrowing capacity on line of credit	250.0
Repayments of lines of credit	185.0	$ 25.0
Long-Term Debt, Gross	175.0		0.0
Letters of credit outstanding, amount	0.0		0.0
Proceeds from borrowing under line of credit	360.0	0.0
Line of Credit Facility [Line Items]
Remaining borrowing capacity on line of credit	75.0		250.0
Letters of credit outstanding, amount	0.0		$ 0.0
Proceeds from borrowing under line of credit	360.0	$ 0.0
Letter of Credit
Debt Instrument
Maximum borrowing capacity on line of credit	$ 20.0